<!DOCTYPE html>
<html>
<head>
    <meta charset='utf-8'>
</head>
<script src="./jquery-1.8.3.min.js"></script>
<script type="text/javascript"> 
var countdown=60; 
function settime(obj) { 
    if (countdown == 0) { 
        obj.removeAttribute("disabled");    
        obj.value="免费获取验证码"; 
        countdown = 60; 
        return;
    } else { 
        obj.setAttribute("disabled", true); 
        obj.value="重新发送(" + countdown + ")"; 
        countdown--; 
    } 
setTimeout(function(){ 
    settime(obj)
    }
    ,1000) 
}
  
</script>
<body> 
<input type="button" id="btn" value="免费获取验证码" onclick="settime(this)" /> 
  
</body>
</html>